U.S. patent number 7,878,282 [Application Number 12/007,774] was granted by the patent office on 2011-02-01 for control device for hybrid vehicle.
This patent grant is currently assigned to Toyota Jidosha Kabushiki Kaisha. Invention is credited to Kenta Kumazaki, Tooru Matsubara, Atsushi Tabata.
United States Patent |
7,878,282 |
Kumazaki , et al. |
February 1, 2011 |
Control device for hybrid vehicle
Abstract
A control device for hybrid vehicle is provided with property
alter means 88 that is operative based on whether or not an EV
running mode is set and alters a given property used for
determining demanded output torque T.sub.OUTt of a transmission
mechanism by referring to an accelerator opening Acc. This
suppresses occurrence of engine startup to meet a requirement for
the EV running mode to be initiated. The property alter means
alters the given property such that during an EV running mode
turn-on state, demanded output torque T.sub.OUTt determined based
on the accelerator opening Acc has a lower value than that set for
an EV running mode turn-off state. That is, this causes a drop in
sensitivity of demanded output torque T.sub.OUTt determined based
on the accelerator opening Acc. Thus, the occurrence of engine
startup induced upon depressive operation of an accelerator pedal
during the EV running mode is suppressed.
Inventors: |
Kumazaki; Kenta (Toyota,
JP), Matsubara; Tooru (Toyota, JP), Tabata;
Atsushi (Okazaki, JP) |
Assignee: |
Toyota Jidosha Kabushiki Kaisha
(Toyota, JP)
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Family
ID: |
39564100 |
Appl.
No.: |
12/007,774 |
Filed: |
January 15, 2008 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20080173485 A1 |
Jul 24, 2008 |
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Foreign Application Priority Data
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Jan 19, 2007 [JP] |
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2007-010844 |
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Current U.S.
Class: |
180/65.265;
180/65.21; 180/65.285; 180/65.27 |
Current CPC
Class: |
B60K
6/445 (20130101); B60K 6/365 (20130101); B60K
6/547 (20130101); F16H 2037/0873 (20130101); Y02T
10/62 (20130101); B60K 1/02 (20130101); Y02T
10/6239 (20130101); F16H 3/728 (20130101); F16H
2200/0043 (20130101); F16H 2200/2041 (20130101); F16H
2200/201 (20130101); B60W 2540/215 (20200201); F16H
2200/0047 (20130101); F16H 2200/2043 (20130101); F16H
2200/2012 (20130101) |
Current International
Class: |
B60W
10/00 (20060101) |
Field of
Search: |
;180/65.25,65.26,65.265,65.285,65.225,65.245,65.8,65.235,65.21,65.27
;701/22,84 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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A 2001-105932 |
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Apr 2001 |
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JP |
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A 2005-178626 |
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Jul 2005 |
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JP |
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A 2005-271618 |
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Oct 2005 |
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JP |
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A 2005-304201 |
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Oct 2005 |
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JP |
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A 2006-180626 |
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Jul 2006 |
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JP |
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Primary Examiner: Phan; Hau V
Attorney, Agent or Firm: Oliff & Berridge, PLC
Claims
What is claimed is:
1. A control device for a hybrid vehicle including an engine and an
electric motor, establishing a motor running state with only the
electric motor serving as a drive-power source, and being switched
to an engine running state with the engine enabled to serve as a
main drive-power source for running the vehicle, if a demanded
drive-force relevant value demanded to the vehicle exceeds a given
value during the motor running state, the control device comprising
relationship alter means for altering a given relationship used in
determining the demanded drive-force relevant value depending on an
output demanded operation amount applied by a driver, by referring
to whether or not a motor running mode demanded for the motor
running state is set.
2. A control device for hybrid vehicle according to claim 1,
wherein the relationship alter means is operative to alter the
given relationship such that the demanded drive-force relevant
value determined based on the output demanded operation amount of
the driver is a lower value when the motor running mode is set,
than in a value appearing when no motor running mode is set.
3. A control device for hybrid vehicle according to claim 1,
wherein the relationship alter means alters the given relationship,
when the motor running mode is set, depending on a vehicle speed
relevant value.
4. A control device for hybrid vehicle according to claim 3,
wherein the relationship alter means alters the given relationship
such that the demanded drive-force relevant value determined based
on the output demanded operation amount of the driver decreases
with a decrease in the vehicle speed relevant value.
5. A control device for hybrid vehicle according to claim 4,
wherein the relationship alter means alters the given relationship
such that with increase of the vehicle speed relevant value, the
demanded drive-force relevant value determined based on the output
demanded operation amount approximates a value of the demanded
drive-force relevant value when no motor running mode is set.
6. A control device for hybrid vehicle according to claim 3,
wherein the vehicle speed relevant value is a relevant value,
corresponding to a vehicle speed representing a speed of the
vehicle in a one to one relationship.
7. A control device for hybrid vehicle according to claim 1,
wherein a drive force relevant value for the demanded drive-force
relevant value is a relevant value, corresponding to a vehicle
drive force with the drive wheels acting on a ground surface in a
one to one relationship.
8. A control device for hybrid vehicle according to claim 1,
wherein the output demanded operation amount is a driver's demand
based on which the demanded drive-force relevant value is
determined.
9. A control device for hybrid vehicle according to claim 1,
wherein the given relationship is a relation between an accelerator
opening and a demanded output torque.
10. A control device for hybrid vehicle according to claim 1,
wherein setting of the motor running mode is determined based on an
manipulation by a driver.
11. A control device for hybrid vehicle according to claim 10,
wherein the manipulation by the driver for setting of the motor
running mode is a turn-on of a motor running mode switch.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to control device for hybrid vehicle, having
an engine and an electric motor, and, more particularly, to a
control device for hybrid vehicle for effectuating switching
between a motor running mode and an engine running mode.
2. Description of the Related Art
A control device for a hybrid vehicle has heretofore been well
known as including an engine and electric motor that enable the
switching between a motor running mode relaying on a drive-power
source composed of only the electric motor, and engine running mode
relaying on another drive-power source mainly composed of the
engine.
For instance, Patent Publication 1 (Japanese Patent Application
Publication No. 2005-304201) discloses a hybrid vehicle having a
control device of such a structure described above. Patent
Publication 1 discloses a technology in which the drive-power
source includes the engine and electric motor and an EV-running
mode is continuously conducted under a situation where during a
motor running mode (EV-running mode), a demanded torque command
value is less than a given EV-drive permit reference value, whereas
when the demanded torque command value exceeds the given EV-drive
permit reference value, the engine is started up to carry out the
engine running mode.
Besides the foregoing, various technologies have heretofore been
known as disclosed in Patent Publication 2 (Japanese Patent
Application Publication No. 2005-271618), Patent Publication 3
(Japanese Patent Application Publication No. 2006-180626), Patent
Publication 4 (Japanese Patent Application Publication No.
2001-105932) and Patent Publication 5 (Japanese Patent Application
Publication No. 2005-178626).
Meanwhile, under a circumstance where a vehicle is traveling on a
road around a residential area or the like with a worrisome engine
sound in concern, a strong demand conceivably occurs for the motor
running mode to be continued for a time period as long as possible.
However, if an accelerator pedal is depressed even on at least
temporary basis, the demanded torque command value increases during
the motor running mode. In this case, it is likely that engine
startup occurs regardless of whether a strong or weak requirement
is present for the motor running mode to be continued.
SUMMARY OF THE INVENTION
The present invention has been completed with the above views in
mind and has an object to provide a control device for a hybrid
vehicle, having an engine and electric motor, which can suppress
the initiation of engine startup to satisfy a request for a motor
running mode to be continued.
To achieve such an object, the invention recited in claim 1, is
featured by a control device for a hybrid vehicle (a) including an
engine and an electric motor, establishing a motor running state
with only the electric motor serving as a drive-power source, and
being switched to an engine running state with the engine enabled
to serve as a main drive-power source for running the vehicle, if a
demanded drive-force relevant value demanded to a vehicle exceeds a
given value during the motor running state, the control device (b)
comprising property alter means for altering a given property used
in determining the demanded drive-force relevant value depending on
an output demanded operation amount applied by a driver, by
referring to whether or not a motor running mode demanded for the
motor running state is set.
With such a structure, the property alter means alters the given
property for use in determining the demanded drive-force relevant
value depending on the output demanded operation amount applied by
the driver, by referring to whether or not the motor running mode
demanded for the motor running state to be initiated is set. This
suppresses an occurrence of engine startup to meet a demand for the
motor running mode to be initiated.
When the motor running mode is set, for instance, the given
property can be altered to allow the demanded drive-force relevant
value determined based on the output demanded operation amount
applied by the driver, to a lower value than the value appearing
when no motor running mode is set. This makes it possible to
decrease a sensitivity of the drive force relevant value determined
based on the output demanded operation amount. As a result, this
enables the suppression of engine startup caused by an increase in
the output demanded operation amount during the motor running
mode.
Preferably, the invention recited in claim 2 is featured by, in the
control device for hybrid vehicle recited in claim 1, the property
alter means which is operative to alter the given property such
that the demanded drive-force relevant value determined based on
the output demanded operation amount of the driver in a lower value
when the motor running mode is set, than in a value appearing when
no motor running mode is set. Such a structure suppresses the
occurrence of engine startup caused by the increase in the output
demanded operation amount during the motor running mode.
Preferably, the invention recited in claim 3 is featured by, in the
control device for hybrid vehicle recited in claim 2, the property
alter means which alters the given property, when the motor running
mode is set, depending on a vehicle speed relevant value. Such a
structure suppresses the occurrence of engine startup in response
to a running condition represented by the vehicle speed relevant
value. For instance, this allows the given property to be altered
such that the demanded drive-force relevant value, determined based
on the output demanded operation amount of the driver, decreases
with a decrease in the vehicle speed relevant value. This
suppresses the occurrence of engine startup during the motor
running mode for the vehicle running at a low vehicle speed in a
residential area or the like with a worrisome engine sound in
concern with an intense demand for the motor running mode to be
continued.
Preferably, the invention recited in claim 4 is featured by, in the
control device for hybrid vehicle recited in claim 3, the property
alter means which alters the given property such that the demanded
drive-force relevant value determined based on the output demanded
operation amount of the driver decreases with a decrease in the
vehicle speed relevant value. Such a structure suppresses the
occurrence of engine startup during the motor running mode for the
vehicle running at a low vehicle speed in a residential area or the
like with a worrisome engine sound in concern with an intense
demand for the motor running mode to be continued.
Preferably, the invention recited in claim 5 is featured by, in the
control device for hybrid vehicle recited in claim 4, the property
alter means which alters the given property such that with increase
of the vehicle speed relevant value, the demanded drive-force
relevant value determined based on the output demanded operation
amount approximates a value of the demanded drive-force relevant
value when no motor running mode is set.
With such a structure, even if the motor running mode is set,
during the running of the vehicle at a middle and high vehicle
speed in an area with an intense demand for power performance to be
obtained, power performance can be obtained at an excellent level
when no motor running mode is set. That is, the motor running mode
can be continuously performed at a low vehicle speed as demanded by
the driver, without sacrificing power performance for the vehicle
to run at the middle and high vehicle speed.
Preferably, as used herein, the term "drive force relevant value",
used for the "demanded drive-force relevant value", refers to a
relevant value (equivalent value), corresponding to a vehicle drive
force (hereinafter referred to as a "drive force") with the drive
wheels acting on for instance the ground surface in the
relationship of one to one (1:1), and the drive force is used as
the drive force relevant value. In addition to the above, use may
be made of for instance torque of a vehicle axle, an output of the
vehicle, output torque of a well-known transmission available to
transmit a drive force of the drive-power source to the drive
wheels, and torque of a propeller shaft.
Preferably, as used herein, the term "output demanded operation
amount" refers to a "driver's demand" based on which, for instance,
the demanded drive-force relevant value is determined. To this end,
use is made of an operation amount of an accelerator device such as
an accelerator pedal or a switch, etc.
Preferably, as used herein, the term "vehicle speed relevant value"
refers to a relevant value (equivalent value), corresponding to for
instance a vehicle speed representing a speed of the vehicle in the
relationship of one to one (1:1). Of course, not only the vehicle
speed is used to represent the vehicle speed relevant value but
also other parameters are used. These may include, for instance, an
output rotation speed of a transmission, a rotation speed of a
vehicle axle, a rotation speed of a propeller shaft and an output
rotation speed of a differential gear device, etc.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a skeleton diagram showing a structure of a drive system
of one embodiment according to the present invention for use in a
hybrid vehicle.
FIG. 2 is a operation diagram table illustrating combined
operations of hydraulically operated frictional coupling devices
for use in performing shifting operations in the vehicular drive
system shown in FIG. 1.
FIG. 3 is a collinear chart indicating mutually relative rotating
speeds for various gear positions in the vehicular drive system
shown in FIG. 1.
FIG. 4 is a view illustrating an electronic control unit with input
and output signals associated therewith which is provided in the
vehicular drive system shown in FIG. 1.
FIG. 5 is a circuit diagram related to linear solenoid valves for
controlling operations of various hydraulic actuators of clutches
C1, C2 and brakes B1 to B3 of a hydraulic control circuit.
FIG. 6 is a view showing one example of a shift operation device
having a shift lever operative to select one of a plurality of
shift positions of multiple kinds.
FIG. 7 is a functional block diagram illustrating major control
functions of the electronic control unit of FIG. 4.
FIG. 8 is a view illustrating one example of a shifting map for use
in performing a shifting control of the drive system.
FIG. 9 is a view illustrating one example of a fuel consumption map
with a broken line representing an optimal fuel consumption curve
of an engine.
FIG. 10 is a view showing a demanded output torque map,
preliminarily obtained on experiments for storage, which represents
one example of a given property for use in determining demanded
output torque of a transmission mechanism based on an accelerator
opening.
FIG. 11 is a view showing one example of a sensitivity function map
between a sensitivity function and a vehicle speed that is
preliminarily obtained on experiments for storage.
FIG. 12A is a view showing one example of a demanded output torque
map with a vehicle speed remaining at a low vehicle speed range
less than a given vehicle speed, and FIG. 12B is a view showing one
example of another demanded output torque map with the vehicle
speed remaining at a middle and high vehicle speed range greater
than the given vehicle speed.
FIG. 13 is a flowchart illustrating a basic sequence of control
operations to be executed by the electronic control unit shown in
FIG. 4, i.e., a basic sequence of control operations to be executed
for suppressing the occurrence of engine startup initiated in
response to a request on an EV running.
FIG. 14 is a skeleton view illustrating a structure of a drive
system of another embodiment according to the present invention for
use in a hybrid vehicle.
FIG. 15 is an operation diagram table, illustrating combined
operations of hydraulically operated frictional coupling devices
for use in performing shifting operations in the vehicular drive
system shown in FIG. 14, which corresponds to the view of FIG.
2.
FIG. 16 is a collinear chart, indicating mutually relative rotating
speeds for various gear positions in the vehicular drive system
shown in FIG. 14, which corresponds to the view of FIG. 3.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Now, various embodiments according to the present invention will be
described below in detail with reference to the accompanying
drawings.
Embodiment 1
First embodiment will be explained with reference to FIGS. 1 to 13.
FIG. 1 is a skeleton diagram for illustrating a transmission
mechanism i.e., shifting mechanism 10 constituting a part of a
drive system for a hybrid vehicle to which the present invention is
applied. As shown in FIG. 1, the transmission mechanism 10 includes
a transmission case 12 (hereinafter referred to as "a case 12")
mounted on a vehicle body as a non-rotary member, an input shaft 14
coaxially disposed inside the case 12 as an input rotary member, an
electrically controlled differential portion 11 (hereinafter
referred to as a "differential portion 11") coaxially connected to
the input shaft 14 either directly, or indirectly via a pulsation
absorbing damper (vibration damping device) not shown, and serving
as a continuously variable transmission portion, an automatic
transmission portion i.e., shifting portion 20 connected in series
in a power transmitting path between the differential portion 11
and drive wheels 34 (see FIG. 7) through a power transmitting
member 18 (power transmitting shaft), and an output shaft 22
connected to the automatic transmission portion 20 and serving as
an output rotary member.
The transmission mechanism 10 may be preferably applied to, for
instance, an FR (front-engine and reverse-drive) type vehicle and
disposed between an engine 8 and a pair of drive wheels 34. The
engine 8 includes an internal combustion engine such as a gasoline
engine or a diesel engine or the like and serves as a drive-power
source, which is directly connected to the input shaft 12 in series
or indirectly through the pulsation absorbing damper (vibration
damping device), not shown. This allows a vehicle drive force to be
transferred from the engine 8 to the pair of drive wheels 34 in
sequence through a differential gear device 32 (final speed
reduction gear) (see FIG. 7) and a pair of drive axles.
With the transmission mechanism 10 of the present embodiment, the
engine 8 and the differential portion 11 are directly connected to
each other. As used herein, the term "directly connected to each
other" refers to a structure under which a direct connection is
established between the associated component parts in the absence
of a fluid-operated power transmitting device such as a torque
converter or fluid coupling device or the like, and a connection
arrangement including, for instance, the pulsation absorbing damper
is involved in the meaning of such a direct connection. Since the
transmission mechanism 10 includes upper and lower halves formed in
a symmetric relation with each other along a central axis, the
lower half is omitted from the skeleton diagram of FIG. 1. This
similarly applies to the other embodiments of the invention
described below.
The differential portion 11 includes a first electric motor M1, a
power distributing mechanism 16 in the form of a mechanical
mechanism serving as a differential mechanism through which an
engine output, applied to the input shaft 14, is mechanically
distributed to the first electric motor M1 and the power
transmitting member 18, and a second electric motor M2 operatively
connected to the power transmitting member 18 for unitary rotation
therewith. In the illustrated embodiment, both the first and second
electric-motors M1 and M2 are comprised of so-called
motor/generators, respectively, each having a function to generate
electric power. The first electric motor M1 has at least a function
to act as a generator (to generate electric power) for generating a
reaction force. The second electric motor M2 has at least a
function as a motor (electric motor) to act as a running
drive-power source to output a vehicle drive force.
The power distributing mechanism 16 is mainly comprised of a first
single-pinion type planetary gear set 24 having a given gear ratio
.rho.1 in the order of, for instance, approximately "0.418". The
first single-pinion type planetary gear set 24 includes rotary
elements (hereinafter referred to as "elements") such as a sun gear
S1, first planet gears P1, a first carrier CA1 rotatably supporting
the planetary gears such that each of the first planet gears P1 is
rotatable about its axis while performing an orbital motion, and a
first ring gear R1 in meshing engagement with the first sun gear S1
via the first planet gears P1. Assume that the first sun gear S1
has a gear teeth of ZS1 and the first ring gear R1 has a gear teeth
of ZR1, the gear ratio .rho.1 is expressed as ZS1/ZR1.
In the power distributing mechanism 16, the first carrier CA1 is
connected to the input shaft 14, i.e., the engine 8, the first sun
gear S1 connected to the first electric motor M1, and the first
ring gear R1 connected to the power-transmitting member 18. With
the power distributing mechanism 16 of such a structure, the first
planetary gear set 24 has the three elements, i.e., the first sun
gear S1, the first planetary gear P1, the first carrier CA1 and the
first ring gear R1 arranged to rotate relative to each other to be
operative for initiating a differential action, i.e., in a
differential state under which the differential action is
initiated. This allows the output of the engine 8 to be distributed
to the first electric motor M1 and the power transmitting mechanism
18. Then, a part of the distributed engine output drives the first
electric motor M1 to generate electric energy, which is stored in
part in a battery, and used in another part to rotatably drive the
second electric motor M2. Thus, the differential portion 11 (power
distributing mechanism 16) is caused to function as an electrically
operated differential device such that, for instance, the
differential portion 11 is placed in a so-called continuously
variable shifting state (electrically established CVT state) to
rotate the power transmitting member 18 at a continuously varying
rate regardless of the engine 8 operating at a given rotation
speed. That is, the differential portion 11 functions as an
electrically controlled continuously variable transmission to
provide a speed ratio .gamma.0 (representing rotation speed
N.sub.IN of the input shaft 14/rotation speed N.sub.18 of the power
transmitting member 18) that is continuously variable from a
minimal value .gamma.0min to a maximal value .gamma.0max.
The automatic transmission portion 20, structured of a
single-pinion type second planetary gear set 26, a single-pinion
type third planetary gear set 28 and a single-pinion type fourth
planetary gear set 30, is of a planetary gear type multiple-step
transmission operative as a step-variable automatic transmission.
The second planetary gear set 26 has a second sun gear S2, second
planet gears P2, a second carrier CA2 supporting the second
planetary gear P2 such that each of the second planet gears P2 is
rotatable about its axis and about the axis of the second sun gear
S2, and a second ring gear R2 meshing with the second sun gear S2
through the second planet gears P2. For example, the second
planetary gear set 26 has a given gear ratio .rho.2 of about
"0.562".
The third planetary gear set 28 has a third sun gear S3, a third
planet gears P3, a third carrier CA3 supporting the third planet
gears P3 such that each of the third planet gears P3 is rotatable
about its axis and about the axis of the third sun gear S3, and a
third ring gear R3 meshing with the third sun gear S3 through the
third planet gears P3. For example, the third planetary gear set 28
has a given gear ratio .rho.3 of about "0.425". The fourth
planetary gear set 30 has a fourth sun gear S4, fourth planet gears
P4; a fourth carrier CA4 supporting the fourth planet gears P4 such
that each of the fourth planet gear P4 is rotatable about its axis
and about the axis of the fourth sun gear S4, and a fourth ring
gear R4 meshing with the fourth sun gear S4 through the fourth
planet gears P4. For example, the fourth planetary gear set 30 has
a given gear ratio p4 of, for instance, about "0.421".
Suppose the second sun gear S2, second ring gear R2, third sun gear
S3, third ring gear R3, fourth sun gear S4 and fourth ring gear R4
have the numbers of gear teeth represented by ZS2, ZR2, ZS3, ZR3,
ZS4 and ZR4, respectively, the gear ratios .rho.2, .rho.3 and
.rho.4 are expressed by ZS2/ZR2, ZS3/ZR3, and ZS4/ZR4,
respectively.
In the automatic transmission portion 20, the second and third sun
gears S2, S3 are integrally connected to each other to be
selectively connected to the power transmitting member 18 through a
second clutch C2 and selectively connected to the casing 12 through
a first brake B1. A second carrier CA2 is selectively connected to
the casing 12 through a second brake B2 and the fourth ring gear R4
is selectively connected to the casing 12 through a third brake B3.
The second ring gear R2, third carrier CA3 and fourth carrier CA4
are integrally connected to each other and connected to the output
shaft 22. The third ring gear R3 and fourth sun gear S4 are
integrally connected to each other and selectively connected to the
power transmitting member 18 through the first clutch C1.
Thus, the automatic transmission portion 20 and the differential
portion 11 (power transmitting member 18) are selectively connected
to each other through the first clutch C1 or the second clutch C2
provided to establish each gear position (shift gear position) in
the automatic transmission portion 20. In other words, the first
and second clutches C1, C2 function as coupling devices i.e.,
engaging device operable to place the power transmitting path
between the power transmitting member 18 and the automatic
transmission portion 20, that is, the power transmitting path
between the differential portion 11 (power transmitting member 18)
and the drive wheels 34, selectively in one of a power transmitting
state in which the vehicle drive force can be transmitted through
the power transmitting path, and the power cut-off state in which
the vehicle drive force cannot be transmitted through the power
transmitting path. That is, with at least one of the first and
second clutches C1 and C2 brought into coupling engagement; the
power-transmitting path is placed in the power transmitting state.
In contrast, uncoupling both the first and second clutches C1 and
C2 places the power-transmitting path in the power cut-off
state.
In the transmission portion 20, uncoupling an on-uncoupling
coupling device while coupling an on-coupling coupling device
allows a so-called "clutch-to-clutch" shifting action to be
executed for selectively establishing one of the gear positions.
This allows a speed ratio .gamma. (representing a ratio of the
rotation speed N.sub.18 of the power transmitting member 18 to the
rotation speed N.sub.OUT of the output shaft 22) to be obtained in
a nearly equal ratio for each gear position. As indicated in the
engagement operation table shown in FIG. 2, for instance, coupling
the first clutch C1 and third brake B3 allows a 1st-speed gear
position to be established at a speed ratio .gamma.1 of
approximately, for instance, "3.357". Coupling the first clutch C1
and second brake B2 allows a 2nd-speed gear position to be
established at a speed ratio .gamma.2 of approximately, for
instance, "2.180" that is less than a value of the gear ratio of
the 1st-speed gear position.
With the first clutch C1 and first brake B1 brought into coupling
engagement, a 3rd-speed gear position is established at a speed
ratio .gamma.3 of, for instance, approximately "1.424" that is less
than a value of the gear ratio of the 2nd-gear position. Coupling
the first clutch C1 and second clutch C2 allows a 4th-speed gear
position to be established at a speed ratio .gamma.4 of, for
instance, approximately "1.000" that is less than a value of the
gear ratio of the 3rd-gear position.
Coupling the second clutch C2 and third brake B3 allows a
reverse-drive gear position (reverse-drive shift position) to be
established at a speed ratio .gamma.R of, for instance,
approximately "3.209" that is intermediate in value between those
of the 1st-speed and 2nd-speed gear positions. Further, uncoupling
the first and second clutches C1, C2 and first to third brakes B1
to B3 results in a consequence of a neutral state "N". In addition,
for the 5th-speed gear position indicated on the operation diagram
table shown in FIG. 2, the automatic transmission portion 20
performs the same coupling operations of the coupling devices as
those achieved for the 4th-speed gear position.
The first clutch C1, second clutch C2, first brake B1, second brake
B2 and third brake B3 (hereinafter collectively referred to as a
"clutch C" and "brake B", unless otherwise specified) are comprised
of hydraulically operated frictional coupling devices that are
often used in a vehicular automatic transmission portion of the
related art. Each of these frictional coupling devices may include
a wet-type multiple-disc clutch, having a plurality of mutually
overlapping friction plates adapted to be pressurized against each
other by a hydraulic actuator, or a band brake including a rotary
drum having an outer circumferential surface on which one band or
two bands are wound with terminal ends being adapted to be
tightened by a hydraulic actuator. Thus, each of the frictional
coupling devices serves to selectively provide a drive connection
between associated two component parts between which such a
coupling device is interposed.
With the transmission mechanism 10 of such a structure, the
differential portion 11, serving as the continuously variable
transmission, and the automatic transmission portion 20 constitute
a continuously variable transmission as a whole. Further,
controlling the differential portion 11 at a fixed speed ratio
enables the differential portion 11 and the automatic transmission
portion 20 to provide the same structure as that of a step-variable
transmission.
More particularly, the differential portion 11 functions as the
continuously variable transmission and the automatic transmission
portion 20, connected to the differential portion 11 in series,
functions as the step-variable transmission, thereby continuously
varying a rotation speed (hereinafter referred to as an "input
rotation speed of the automatic transmission portion 20"), i.e., a
rotation speed of the power transmitting member 18 (hereinafter
referred to as a "transmitting-member rotation speed N.sub.18")
input to the automatic transmission portion 20 for at least one
gear position "M". This enables the gear position "M" to have a
continuously variable range in speed ratio. Accordingly, the
transmission mechanism 10 provides an overall speed ratio .gamma.T
(representing a ratio of the rotation speed N.sub.IN of the input
shaft 14 to the rotation speed N.sub.OUT of the output shaft 22) in
a continuously variable range. Thus, the transmission mechanism 10
can establish the continuously variable transmission. The overall
speed ratio .gamma.T of the transmission mechanism 10 is a total
speed ratio .gamma.T of the automatic transmission portion 20 as a
whole that is established depending the speed ratio .gamma.0 of the
differential portion 11 and the speed ratio .gamma. of the
automatic transmission portion 20.
For the respective gear positions such as, for instance, the
1st-speed to 4th-speed gear positions of the automatic transmission
portion 20 and the reverse-drive gear position as indicated in the
engagement operation table shown in FIG. 2, the
power-transmitting-member rotation speed N.sub.18 is continuously
variable such that each gear position is obtained in a continuously
variable speed range. Accordingly, a speed ratio between the
adjacent gear positions becomes infinitely and continuously
variable, enabling the total speed ratio .gamma.T to be obtained in
an infinitely variable range with the transmission mechanism 10 as
a whole.
Controlling the differential portion 11 at a fixed speed ratio
.gamma.0 and selectively coupling the clutch C and brake B causes
either one of the 1st-speed to 4th-speed gear positions or the
reverse-drive gear position (reverse-drive shift position) to be
selectively established. This allows the transmission mechanism 10
to have the overall speed ratio .gamma.T in a nearly equal ratio
for each of the gear positions. Thus, the transmission mechanism 10
can be established in the same state as that of the step-variable
transmission.
If, for instance, the differential portion 11 is controlled so as
to provide the speed ratio .gamma.0 at a fixed value of "1", the
transmission mechanism 10 provides the total speed ratio .gamma.T
for each gear position of the 1st-speed to 4th-speed gear positions
and reverse-drive gear position of the automatic transmission
portion 20 as indicated by the engagement operation table shown in
FIG. 2. Further, if the automatic transmission portion 20 is
controlled under the 4th-speed gear position so as to cause the
differential portion 11 to have the fixed speed ratio .gamma.0 of
approximately, for instance, "0.7" less than a value of "1", the
automatic transmission portion 20 has the total speed ratio
.gamma.T of approximately, for instance, "0.705" that is less than
a value of the 4th-speed gear position as indicated by a 5th-speed
gear position as indicated by the engagement operation table shown
in FIG. 2.
FIG. 3 is a collinear chart for the transmission mechanism 10,
including the differential portion 11 and the automatic
transmission portion 20, wherein the relative motion relationships
among the rotation speeds of the various rotary elements in
different coupling states for each gear position can be plotted on
straight lines. The collinear chart of FIG. 3 takes the form of a
two-dimensional coordinate system having the abscissa axis plotted
with the gear ratios .rho. of the planetary gear sets 24, 26, 28,
30 and the ordinate axis plotted with the mutually relative
rotating speeds of the rotary elements. Among transverse lines, a
transverse line X1 on a lower area indicates a rotation speed
laying at a zeroed level; a transverse line X2 on an upper area
indicates a rotation speed of "1.0", that is, a rotating speed
N.sub.E of the engine 8 connected to the input shaft 14; and a
transverse line XG indicates a rotation speed of the power
transmitting member 18.
Starting from the left in sequence, three vertical lines Y1 to Y3,
associated with the three elements of the power distributing
mechanism 16 forming the differential portion 11, represent the
mutually relative rotating speeds of the first sun gear S1
corresponding to a second rotary element (second element) RE2, the
first carrier CA1 corresponding to a first rotary element (first
element) RE1, and the first ring gear R1 corresponding to a third
rotary element (third element) RE3, respectively. A distance
between the adjacent vertical lines is determined based on the gear
ratio .rho.1 of the first planetary gear set 24.
Starting from the left in sequence, further, five vertical lines Y4
to Y8 for the automatic transmission portion 20 represent the
mutually relative rotating speeds of: the second and third sun
gears S2, S3, corresponding to a fourth rotary element (fourth
element) RE4 and connected to each other; the second carrier CA2
corresponding to a fifth rotary element (fifth element) RE5; the
fourth ring gear R4a corresponding to a sixth rotary element (sixth
element) RE6; the second ring gear R2, third carrier CA3 and fourth
carrier CA4 corresponding to a seventh rotary element (seventh
element) RE7 and connected to each other; and the third ring gear
R3 and fourth sun gear S4 corresponding to an eighth rotary element
(eighth element) RE8, respectively, and connected to each other.
Each distance between the adjacent vertical lines is determined
based on the gear ratios .rho.2, .rho.3 and .rho.4 of the second,
third and fourth planetary gear sets 26, 28, 30.
In the relationship among the vertical lines on the collinear
chart, if a space between the sun gear and carrier is set to a
distance corresponding to a value of "1", then, a space between the
carrier and ring gear lies at a distance corresponding to the gear
ratio .rho. of the planetary gear set. That is, for the
differential portion 11, a space between the vertical lines Y1 and
Y2 is set to a distance corresponding to a value of "1" and a space
between the vertical lines Y2 and Y3 is set to a distance
corresponding to the gear ratio .rho.1. For the automatic
transmission portion 20, further, a space between the sun gear and
carrier is set to a distance corresponding to a value of "1" for
each of the second, third and fourth planetary gear sets 26, 28, 30
with the space between the carrier and ring gear being set to the
distance corresponding to the gear ratio .rho.1.
To describe the transmission mechanism 10 with reference to the
collinear chart of FIG. 3, with the power distributing mechanism 16
(differential portion 11), the first rotary element RE1 (first
carrier CA1) of the first planetary gear set 24 is connected to the
input shaft 14, i.e., the engine 8. The second rotary element RE2
is connected to the first electric motor M1. The third rotary
element RE3 (first ring gear R1) is connected to the power
transmitting member 18 and second electric motor M2. Thus, the
transmission mechanism 10 is structured so as to allow the input
shaft 14 to transmit (input) a rotary motion to the automatic
transmission portion 20 through the power transmitting member 18.
With such a structure, the relationship between the rotation speeds
of the first sun gear S1 and the first ring gear R1 is represented
by an inclined straight line L0 which passes across a point of
intersection between the lines Y2 and X2.
Now, description is made of a case in which, for example, the
differential portion 11 is placed in a differential state with the
first to third rotary elements RE1 to RE3 enabled to rotate
relative to each other and the rotation speed of the first ring
gear R1, indicated at an intersecting point between the straight
line L0 and the vertical line Y3, is bound with the vehicle speed V
and remains at a nearly constant level. In this case, as the
rotation speed of the first electric motor M1 is controlled to
raise or lower the rotation speed of the first sun gear S1
indicated at an intersecting point between the straight line L0 and
the vertical line Y1, the rotation speed of the first carrier CA1,
i.e., the engine rotation speed N.sub.E, indicated by an
intersecting pint between the straight line L0 and the vertical
line Y2, is raised or lowered.
By controlling the rotation speed of the first electric motor M1 so
as to cause the speed ratio .gamma.0 of the differential portion 11
to be fixed at "1", the first sun gear S1 rotates at the same speed
as the engine rotation speed N.sub.E. Then, the straight line L0 is
aligned with the horizontal line X2 and the first ring gear R1,
i.e., the power transmitting member 18, is caused to rotate at the
same speed as the engine rotation speed N.sub.E. On the contrary,
if the rotation speed of the first electric motor M1 is controlled
so as to allow the differential portion 11 to have the speed ratio
.gamma.0 of approximately, for instance, "0.7" less than a value
less than "1". This causes the rotation speed of the first sun gear
S1 to be zeroed. Then, the straight line L0 assumes a state shown
in FIG. 3 in which the power-transmitting member rotation speed
N.sub.18 increases to a higher level than the engine rotation speed
N.sub.E.
With the automatic transmission portion 20, the fourth rotary
element RE4 is selectively connected to the power transmitting
member 18 via the second clutch C2 and selectively connected to the
casing 12 via the first brake B1. The fifth rotary element RE5 is
selectively connected to the casing 12 via the second brake B2. The
sixth rotary element RE6 is selectively connected to the casing 12
via the third brake B3. The seventh rotary element RE7 is connected
to the output shaft 22 and the eighth rotary element RE8 is
selectively connected to the power transmitting member 18 via the
first clutch C1.
In the automatic transmission portion 20, the differential portion
11 is placed in a state with the straight line L0 brought into
coincidence with the horizontal line X2. In this moment, the
differential portion 11 transfers the vehicle drive force to the
eighth rotary element RE8 at the same speed as the engine rotation
speed N.sub.E. Then, as the first clutch C1 and third brake B3 are
coupled, the rotation speed of the output shaft 22 is indicated for
the 1st-speed gear position. This is represented by an intersecting
point between the inclined line L1, passing across an intersecting
point between the vertical line Y8, indicative of the rotation
speed of the eighth rotary element RE8, and the horizontal line X2
and a point of intersection between the vertical line Y6,
indicative of the rotation speed of the sixth rotary element RE6,
and the horizontal line. X1, and an intersecting point intersecting
the vertical line Y7 indicative of the rotation speed of the
seventh rotary element RE connected to the output shaft 22 as
indicated in FIG. 3.
Similarly, the rotation speed of the output shaft 22 is indicated
for the 2nd-speed gear position as represented by an intersecting
point between an inclined straight line L2, determined when the
first clutch C1 and second brake B2 are coupled, and the vertical
line Y7 indicative of the rotation speed of the seventh rotary
element RE7 connected to the output shaft 22. The rotation speed of
the output shaft 22 is indicated for the 3rd-speed gear position as
represented by an intersecting point between an inclined straight
line L3, determined when the first clutch C1 and first brake B1 are
coupled, and the vertical line Y7 indicative of the rotation speed
of the seventh rotary element RE7 connected to the output shaft 22.
The rotation speed of the output shaft 22 is indicated for the
4th-speed gear position as represented by an intersecting point
between a horizontal straight line L4, determined with the first
clutch C1 and second clutch C2 being coupled, and the vertical line
Y7 indicative of the rotation speed of the seventh rotary element
RE7 connected to the output shaft 22.
With the differential portion 11, if the straight line L0 is caused
to assume a position shown in FIG. 3, the differential portion 11
transmits the rotary motion to the eighth rotary element RE8 at a
rotation speed higher than the engine rotation speed N.sub.E. Under
such a state, as shown in FIG. 3, the rotation speed of the output
shaft 22 is indicated for the 5th-speed gear position as
represented by an intersecting point between a horizontal straight
line L5 determined with the first and second clutches C1, C2 being
coupled, and the vertical line Y7 indicative of the rotation speed
of the seventh rotary element RE7 connected to the output shaft
22.
FIG. 4 shows an electronic control unit 80, operative to control
the transmission mechanism 10 of the present invention, which is
applied with various input signals and outputs various signals in
response thereto. The electronic control unit 80 includes a
so-called microcomputer incorporating a CPU, a ROM, a RAM and an
input/output interface. The microcomputer processes the signals
according to programs stored in the ROM while utilizing a temporary
data storage function of the ROM, thereby implementing hybrid drive
controls of the engine 8 and electric motors M while executing
drive controls such as shifting controls of the automatic
transmission portion 20.
The electronic control unit 80, connected to various sensors and
switches as shown in FIG. 4, receives various signals including a
signal indicative of an engine coolant temperature TEMP.sub.W, a
signal indicative of a shift position P.sub.SH and a signal
indicative of the number of operations initiated on an "M" position
of a shift lever 52 (see FIG. 6), a signal indicative of the engine
rotation speed N.sub.E representing the rotation speed of the
engine 8, a signal indicative of the presence or absence of a
switching operation initiated for setting a motor drive (EV drive)
mode, a signal indicative of a gear train preset value, a signal
commanding an M mode (manual shift running mode); a signal
indicative of an air conditioner being turned on, a signal
indicative of the vehicle speed V corresponding to the rotation
speed (hereinafter referred to as "output shaft rotation speed")
N.sub.OUT of the output shaft 22, a signal indicative of a
temperature T.sub.OIL of working oil of the automatic transmission
portion 20, a signal indicative of a side brake under operation, a
signal indicative of a foot brake under operation, and a signal
indicative of a foot brake being actuated.
The various signals further includes a signal indicative of a
temperature of a catalyst, a signal indicative of an accelerator
opening Acc representing an operating stroke of an accelerator
pedal corresponding to an output demanded operation amount intended
by a driver, a signal indicative of a cam angle, a signal
indicative of a snow mode being set, a signal indicative of a fore
and aft acceleration value G of the vehicle, a signal indicative of
an auto-cruising running mode, a signal indicative of a weight
(vehicle weight) of the vehicle, a signal indicative of a wheel
velocity of each drive wheel, a signal indicative of a rotation
speed N.sub.M1 of the first electric motor M1 (hereinafter referred
to as "first-motor rotation speed N.sub.M1), a signal indicative of
a rotation speed N.sub.M2 of the second electric motor M2
(hereinafter referred to as "second-motor rotation speed N.sub.M2),
and a signal indicative of a state of charge (charged state) SOC of
a battery 60 (see FIG. 7), etc.
Meanwhile, the electronic control unit 80 generates various output
signals to be applied to an engine output control device 58 (see
FIG. 7) for controlling an output of the engine 8. These output
signals include, for instance, a drive signal to be applied to a
throttle actuator 64 for controlling a throttle valve opening
.theta..sub.TH of an electronic throttle valve 62 disposed in an
intake manifold 60 of the engine 8, a fuel supply quantity signal
to be applied to a fuel injecting device 66 for controlling an
amount of fuel injected into the intake manifold 60 or cylinders of
the engine 8, and an ignition signal to be applied to an ignition
device 68 to control the ignition timing of the engine 8.
The output signals further include, for instance, a supercharger
pressure regulation signal for regulating a supercharger pressure
of the engine 8, command signals for commanding the operations of
the electric motors M, an EV running mode display signal providing
a display that an EV running mode is set, a shift-position
(manipulated position) display signal for actuating a shift-range
indicator, a gear-ratio display signal for displaying the gear
ratio, and a snow-mode display signal for displaying the presence
of a snow-mode.
In addition, the output signals include, for instance, an ABS
actuation signal for actuating an ABS actuator to preclude
slippages of the drive wheels during a braking phase, an M-mode
display signal for displaying the M-mode being selected, valve
command signals for actuating electromagnetic valves (linear
solenoid valves), incorporated in the hydraulic control unit 70
(see FIGS. 5 and 7) for controlling the hydraulic actuators of the
hydraulically operated frictional coupling devices of the
differential portion 11 and automatic transmission portion 20, a
signal for causing regulator valves (pressure regulator valves),
incorporated in the hydraulic control unit 70, to regulate a line
pressure P.sub.L, a drive command signal for actuating an
electrically driven hydraulic pump acting as a hydraulic
original-pressure source for the line pressure P.sub.L to be
regulated, a signal applied to a cruise control computer, and an
electric air-conditioner drive signal for driving an electric
air-conditioner, etc.
FIG. 5 is a circuit diagram related to linear solenoid valves SL1
to SL5 of the hydraulic control circuit 70 for controlling the
operations of respective hydraulic actuators (hydraulic cylinders)
AC1 and AC2 and AB1 to AB3 of the clutches C1, C2 and brakes B1 to
B3.
In FIG. 5, the line pressure P.sub.L is applied to the respective
linear solenoid valves SL1-SL5, connected to hydraulic actuators
AC1 and AC2 and AB1 to AB3, respectively. These linear solenoids
are controlled in response to command signals delivered from the
electronic control unit 80, thereby regulating the line pressure PL
into respective clutch engaging pressures PC1 and PC2 and PB1 to
PB3 which in turn are directly supplied to the respective hydraulic
actuators AC1 and AC2 and AB1 to AB3. The original hydraulic
pressure, generated by the electrical oil pump (not shown) or a
mechanical oil pump rotatably driven by the engine 30, is regulated
by, for instance, a relief-type pressure regulator valve to adjust
the line pressure P.sub.L depending on a load of the engine 8 or
the like represented in terms of the accelerator opening or
throttle valve opening.
The linear solenoid valves SL1 to SL5, fundamentally formed in
identical structures, are independently energized or de-energized
with the electronic control unit 80. This allows the hydraulic
actuators AC1 and AC2 and AB1 to AB3 to independently and
controllably regulate respective hydraulic pressures, thereby
controlling the clutch engaging pressures PC1 and PC2 and PB1 to
PB3 for the clutches C1, C2 and brakes B1 to B3.
With the automatic transmission portion 20, predetermined coupling
devices are coupled in a manner as indicated on, for instance, the
engagement operation table shown in FIG. 2, thereby establishing
various gear positions. In addition, during the shifting control of
the automatic transmission portion 20, a so-called clutch-to-clutch
shifting is executed to simultaneously control the coupling or
uncoupling states of the clutches C and brakes B relevant to the
shifting operations.
FIG. 6 is a view showing one example of a shift operation device 50
serving as a changeover device operative to select one of shift
positions P.sub.SH multiple kinds on manual operation. The shift
operation device 50 is mounted in, for instance, an area lateral to
a driver's seat and includes a shift lever 52 to be manipulated for
selecting one of the multiple shift positions P.sub.SH.
The shift lever 52 has a structure to manually select one of a
parking position "P (Parking)", a reverse drive position "R
(Reverse)", a forward-drive automatic running position "D (Drive)"
and a forward-drive manual-shift position "M (Manual)". In the
Parking, an inside of the transmission mechanism 10, i.e., the
power transmitting path inside the automatic transmission portion
20 is shut off in a neutral condition, i.e., a neutral state with
the output shaft 22 of the automatic transmission portion 20
remained under a locked state. In the Reverse, a neutral position
"N (Neutral)" under which the power-transmitting path inside the
transmission mechanism 10 is shut off under the neutral state.
In the Drive, an automatic shift mode is initiated within a varying
range of a shiftable total speed ratio .gamma.T of the transmission
mechanism 10 to be obtained with various gear positions attained on
the automatic shift control performed in an infinitely variable
speed ratio range of the differential portion 11 upon the
establishment of the automatic shift mode and a range of the
1st-speed to the 4th-speed gear positions of the automatic
transmission portion 20. In the Manual, a manual-shift running mode
(manual mode) is established to set a so-called shift range to
limit a shift gear position on a high speed range during the
operation of the automatic transmission portion 20 under the
automatic shift control.
As the shift lever 52 is shifted to the various shift positions
P.sub.SH, for instance, the hydraulic control circuit 70 is
electrically switched in conjunction with the manual operation of
the shift lever 52, thereby establishing the reverse-drive gear
position "R", the neutral position "N" and the various gear
positions of the forward-drive gear position "D".
Among the respective shift positions P.sub.SH indicated by the "P"
to "M" positions, the "P" and "N" positions represent non-running
positions, selected when no vehicle is intended to run, under which
both the first and second clutches C1, C2 are uncoupled as
indicated in, for instance, the engagement operation table shown in
FIG. 2. That is, the non-running positions represent non-drive
positions enabling the first and second clutches C1, C2 to be
selected to place the power transmitting path in a power cut-off
state such that the power transmitting path of the automatic
transmission portion 20 is shut off to disenable the driving of the
vehicle.
The "R", "D" and "M" positions represent running positions selected
when the vehicle is caused to run. That is, at least one of the
first and second clutches C1, C2 is coupled as indicated in, for
instance, the engagement operation table shown in FIG. 2. That is,
these running positions represent drive positions under which the
first and/or second clutches C1, C2 are selected to switch the
power transmitting path to a power transmitting state such that the
power transmitting path of the automatic transmission portion 20 is
connected to enable the driving of the vehicle.
More particularly, the shift lever 52 is manually shifted from the
"P" position or "N" position to the "R" position. This causes the
second clutch C2 to be coupled causing the power transmitting path
of the automatic transmission portion 20 to be switched from the
power cut-off state to the power transmitting state. With the shift
lever 52 manually shifted from the "N" position to the "D"
position, at least the first clutch C1 is coupled to switch the
power transmitting path of the automatic transmission portion 20
from the power cut-off state to the power transmitting state.
With the shift lever 52 manually shifted from the "R" position to
the "P" or "N" position, the second clutch C2 is uncoupled to
switch the power transmitting path of the automatic transmission
portion 20 from the power transmitting state to the power cut-off
state. With the shift lever 52 manually shifted from the "D"
position to the "N" position, the first and second clutches C1, C2
are uncoupled to switch the power transmitting path of the
automatic transmission portion 20 from the power transmitting state
to the power cut-off state.
FIG. 7 is a functional block diagram illustrating major control
functions to be executed by the electronic control unit 80. In FIG.
7, step-variable shift control means 82 determines whether to
execute a shifting, i.e., a gear position to be shifted in the
automatic transmission portion 20 based on a vehicle condition by
referring to the relationships (shifting lines and shifting map)
shown in FIG. 8. Then, the automatic transmission portion 20 is
caused to execute the automatic shift control so as to establish a
gear position resulting from the determination. Also, FIG. 8 shows
upshift lines (in solid lines) and downshift lines (in single dot
lines) that are preliminarily stored in terms of parameters such as
the vehicle speed V and output torque T.sub.OUT of the automatic
transmission portion 20. The vehicle condition is represented with
an actual vehicle speed V and demanded output torque T.sub.OUT of
the transmission mechanism 10.
When this takes place, the step-variable shift control means 82
outputs commands (a shift output command and a hydraulic pressure
command) to the hydraulic control circuit 70 for operating the
hydraulically operated frictional coupling devices, involved in the
shifting of the automatic transmission portion 20, in coupling
i.e., engaged and/or uncoupling i.e., disengaged or released states
so as to establish the gear positions in accordance with the
engagement operation table shown in FIG. 2. These commands include
a command for uncoupling on-uncoupling side coupling devices
involved in the shifting of the automatic transmission portion 20,
and a command for coupling on-coupling side coupling devices to
cause the clutch-to-clutch shifting to be executed. Upon receipt of
such commands, the hydraulic control circuit 70 actuates the linear
solenoid valves SL of the hydraulic control circuit 70 so as to
uncouple, for instance, the on-uncoupling coupling devices,
involved in the shifting of the automatic transmission portion 20,
while coupling the on-coupling coupling devices for thereby
executing the shifting of the automatic transmission portion
20.
Hybrid control means 84 controls a speed ratio .gamma.0 of the
differential portion 11 actuating as an electrically controlled
continuously variable transmission. That is, the hybrid control
means 84 causes the engine 8 to operate in an operating range at a
high efficiency while causing the drive forces of the engine 8 and
the second electric motor M2 to be distributed at optimal rates and
causing a reacting force of the first electric motor M1 to
optimally vary during the operation thereof to generate electric
power. At a vehicle speed V during the running of the vehicle in
one occasion, for instance, the hybrid control means 84 calculates
a target (demanded) output for the vehicle based on the accelerator
opening Acc representing the output demanded operation amount
intended by the driver, thereby calculating a demanded total target
output based on the target output of the vehicle and a battery
charge demanded value. In this moment, a target engine output is
calculated in consideration of a loss in power transmission, loads
of auxiliary units, assist torque of the second electric motor M2
or the like so as to obtain the total target output. Then, the
hybrid control means 84 controls the engine 8, while controlling a
rate of driving the first electric motor M1 to generate electric
power, so as to obtain the engine rotation speed N.sub.E and engine
torque T.sub.E such that the target engine output is obtained.
The hybrid control means 84 executes such controls in consideration
of, for instance, the gear position of the automatic transmission
portion 20 with a view to increasing a dynamic performance and
improving fuel consumption. During such hybrid controls, the
differential portion 11 is caused to function as the electrically
controlled continuously variable transmission such that the engine
rotation speed N.sub.E and vehicle speed V, determined for the
engine 8 to operate in the operating range at a high efficiency,
match the rotation speed of the power transmitting member 18
determined with the vehicle speed V and gear position of the
automatic transmission portion 20.
That is, the hybrid control means 84 determines a target value of
the total speed ratio .gamma.T of the transmission mechanism 10 so
as to cause the engine 8 to operate on an optimal fuel efficiency
curve (a fuel efficiency map and the relationships) of the engine
8, as indicated by a dotted line in FIG. 9. The optimal fuel
efficiency curve is preliminarily obtained on experiments and
prestored to provide a compromise between driveability and fuel
consumption during the running of the vehicle under a continuously
variable shifting mode on a two-dimensional coordinate established
with the engine rotation speed N.sub.E and output torque (engine
torque) T.sub.E of the engine 8.
For instance, the target value of the total speed ratio .gamma.T of
the transmission mechanism 10 is determined so as to obtain engine
torque T.sub.E and engine rotation speed N.sub.E at respective
values for generating the engine output needed for the target
outputs (a total target output and demanded drive force) to be
satisfied. To obtain such target values, the speed ratio .gamma.0
of the differential portion 11 is controlled in consideration of
the gear position in the automatic transmission portion 20, thereby
controlling the total speed ratio .gamma.T within a shiftable
varying range.
When this takes place, the hybrid control means 84 allows electric
energy, generated by the first electric motor M1, to be supplied
through an inverter 54 to a battery 56 and the second electric
motor M2. Thus, a major part of the drive force of the engine 8 is
mechanically transferred to the power transmitting member 18.
However, a remaining part of the drive force of the engine 8 is
consumed with the first electric motor M1 to generate electric
power for conversion into electric energy. Resulting electric
energy is supplied through the inverter 54 into the second electric
motor M2, which is consequently driven to generate a drive force
that is transmitted to the power transmitting member 18. Thus, an
electric path is established by equipment, involved in operations
including the step of generating electric power to the step of
causing the second electric motor M2 to consume resultant electric
energy, in which the part of the drive force of the engine 8 is
converted into electric energy which in turn is converted into
mechanical energy.
The hybrid control means 84 allows the differential portion 11 to
perform an electrically controlled CVT function to control, for
instance, the first-motor rotation speed N.sub.M1. This causes the
engine rotation speed N.sub.E to be maintained at a nearly fixed
level or to be controlled at an arbitrary rotation speed regardless
of the vehicle remaining under a halted condition or a running
condition. In other words, the hybrid control means 84 maintains
the engine rotation speed N.sub.E at the nearly fixed level or
controls the same at the arbitrary rotation speed while rotatably
controlling the first-motor rotation speed N.sub.M1 at an arbitrary
rotation speed.
When raising, for instance, the engine rotation speed N.sub.E
during the running of the vehicle, the hybrid control means 84
raises the first-motor rotation speed N.sub.M1 while maintaining a
second-motor rotation speed N.sub.M2 at a nearly fixed level that
is bound with the vehicle speed V (represented by wheel velocities
of the drive wheels 34) as will be apparent from the collinear
chart shown in FIG. 3. Further, in order for the engine rotation
speed N.sub.E to be maintained at a nearly fixed level during the
shifting of the automatic transmission portion 20, the hybrid
control means 84 varies the first-motor rotation speed N.sub.M1 in
a direction opposite to that in which the second-motor rotation
speed N.sub.M2 varies with the shifting of the automatic
transmission portion 20 while maintaining the engine rotation speed
N.sub.E at the nearly fixed level.
The hybrid control means 84 functionally includes engine output
control means for executing the output control of the engine 8 so
as to cause the same to generate a demanded engine output. In
particular, the hybrid control means 84 causes the throttle
actuator 64 to controllably open or close the electronic throttle
valve 62 for performing a throttle control. In addition, the hybrid
control means 84 outputs commands singly or in combination to an
engine output control device 58. This causes a fuel injection
device 66 to control a fuel injection quantity and a fuel injection
timing for a fuel injection control while permitting an ignition
device 68 such as an igniter or the like to control an ignition
timing for an ignition timing control.
The hybrid control means 84 is enabled to execute a motor drive (EV
drive) mode under which with the engine 8 halted in operation, the
second electric motor M2 is driven with electric power, delivered
from the battery 56, and serves as a drive-power source comprised
of only the second electric motor M2.
For instance, the hybrid control means 84 includes demanded
drive-force relevant value calculation means 86 for calculating
demanded output torque T.sub.OUTt based on an actual accelerator
opening Acc by referring to a given property, used to determine
demanded output torque T.sub.OUTt of the transmission mechanism 10
depending on the accelerator opening Acc. As used herein, the term
"given property" refers to the relationship (demanded output torque
map) between the accelerator opening Acc, preliminarily obtained on
experiments and prestored, and demanded output torque T.sub.OUTt as
shown, for instance, in FIG. 10. When demanded output torque
T.sub.OUTt, calculated by the demanded drive-force relevant value
calculation means 86, is less than a given value T.sub.OUTt, the EV
running mode is executed. In contrast, if demanded output torque
T.sub.OUTt exceeds the given value T.sub.OUT1 during the EV running
mode, the EV running mode is switched to an engine running mode. In
this case, the vehicle is caused to run with a drive-power source
mainly comprised of the engine 8. As used herein, the term "given
value T.sub.OUT1" refers to an EV drive permit value that is
preliminarily determined on experiments for determining whether to
execute the switching from the motor running mode to the engine
running mode in consideration of, for instance, output torque of
the second electric motor M2.
In FIG. 10, a hatched area represents an EV running region for the
EV running mode to be executed with demanded output torque
T.sub.OUTt remained less than the given value T.sub.OUT1. A blank
area above the hatched area represents an engine running region for
the engine 8 to start up to initiate the engine running mode with
demanded output torque T.sub.OUTt exceeding the given value
T.sub.OUT1. Thus, the hybrid control means 84 executes the EV
running mode at relatively low output torque T.sub.OUT, i.e., low
engine torque T.sub.E at which the engine 8 is regarded to have a
lower engine efficiency than that of the engine 8 operating in a
high torque range. From another point of view, the hybrid control
means 84 executes the EV running mode within a range for the second
electric motor M2 to be available to be driven.
The hybrid control means 84 places, for instance, the first
electric motor M1 in an unloaded condition for idling while causing
the differential portion 11 to initiate the electrically controlled
CVT function (differential action) depending on needs such that the
engine rotation speed N.sub.E is zeroed or nearly zeroed. This is
because such a control minimizes a drag of the engine 8 remaining
under a halted condition, thereby improving fuel consumption during
the EV running mode.
To perform the switching between the engine running mode and motor
running mode, the hybrid control means 84 functionally includes
engine-startup stop control means that switches an operating state
of the engine 8 between an operative state and a halted state,
i.e., starts up or halts the engine 8.
Now, description is made of a situation under which an accelerator
pedal is deeply depressed beyond a given accelerator opening Acc1
(see FIG. 10) and demanded output torque T.sub.OUT exceeds the
given value T.sub.OUT1. Under such a situation, a vehicle condition
is caused to vary from the EV running region to the engine running
region. In this case, the engine-startup stop control means
determines that the vehicle condition is switched from the EV
running region to the engine running region. This corresponds to a
situation where engine start (startup) is determined.
In such a case, the hybrid control means 84 turns on the first
electric motor M1 to raise the first-motor rotation speed N.sub.M1,
rendering the first electric motor M1 operative as a starter. This
increases the engine rotation speed N.sub.E to a value beyond a
given rotation speed N.sub.E' enabling complete combustion. At the
same time, the fuel injection device 66 supplies (injects) fuel
into a combustion chamber at the engine rotation speed N.sub.E
beyond the given rotation speed N.sub.E', i.e., for instance, at an
autonomously rotatable engine rotation speed N.sub.E beyond an
idling rotation speed. Thereafter, the ignition device 68 ignites
an air-fuel mixture in the combustion chamber, causing the engine 8
to start up. Thus, the vehicle condition is shifted from the EV
running mode to the engine running mode.
Meanwhile, if the accelerator pedal is released to a level less
than the given accelerator opening Acc1 (FIG. 10) and demanded
output torque T.sub.OUT becomes less than the given value
T.sub.OUT1, the hybrid control means 84 operates in a manner
described below. Under such a situation, the vehicle condition is
caused to vary from the EV running region to the engine running
region, and the hybrid control means 84 determines that the vehicle
condition is switched from the EV running mode to the engine
running mode. This corresponds to a case in which the engine halt
is determined. In such a case, the hybrid control means 84 allows
the fuel injection device 66 to stop the supply of fuel, i.e., to
cut off the supply of fuel. This results in a halt of the engine 8,
thereby switching the vehicle condition from the engine running
mode to the EV running mode.
During the engine running mode, the hybrid control means 84
establishes the electric path under which the second electric motor
M2 is supplied with electric energy delivered from the first
electric motor M1 and/or electric energy delivered from the battery
56. This causes the second electric-motor M2 to be driven, thereby
providing torque to the drive wheels 34. This makes it possible to
effectuate a so-called torque assist for assisting drive power of
the engine 8. Therefore, in the illustrated embodiment, the engine
running mode involves a phase covering both the engine running mode
and EV running mode.
The hybrid control means 84 renders the first electric motor M1
inoperative under the unloaded condition, thereby permitting free
rotation, i.e., idling operation. This causes the differential
portion 11 to have the same state as that in which torque transfer
is disenabled, i.e., a state in which the power transmitting path
of the automatic transmission portion 20 is interrupted with no
output being delivered from the differential portion 11. That is,
upon rendering the first electric motor M1 inoperative under the
unloaded condition, the hybrid control means 84 makes it possible
to place the differential portion 11 in a neutral state (neutral
condition) with the power transmitting path being electrically
interrupted.
Under a circumstance where the vehicle runs in a residential area
or the like with a worrisome engine sound in concern, it is
conceived that a strong requirement occurs for the EV running mode
to be continued as far as possible. However, during the EV running
mode, if the accelerator pedal is depressed even for a temporary
time period with a resultant increase of demanded output torque
T.sub.OUT beyond the given value T.sub.OUT, it is likely that the
engine 8 starts up regardless of the strong requirement for the EV
running mode to be continued. As used herein, the expression
"circumstance with strong requirement occurs for the EV running
mode to be continued" is supposed to involve a situation under
which, for instance, the driver turns on an EV running mode switch
72 (see FIG. 4) to set the EV running mode requiring the EV running
mode to be initiated.
To this end, the control device of the present embodiment includes
property alter means 88, operative depending on whether or not the
EV running mode is set, which alters a given property used in
determining demanded output torque T.sub.OUTt of the transmission
mechanism 10 based on the accelerator opening Acc.
More particularly, EV running mode determination means 90 operates
based on whether or not, for instance, the EV running mode switch
72 is turned on, thereby determining whether or not the EV running
mode is set.
In the illustrated embodiment, it is supposed that an EV running
mode turn-on state corresponds to a phase in which the EV running
mode determination means 90 determines that the EV running mode is
set. Likewise, an EV running mode turn-off state is supposed to
correspond to a phase in which the EV running mode determination
means 90 determines that no EV running mode is set.
The property alter means 88 alters the given property such that for
the EV running mode turn-on state, demanded output torque
T.sub.OUTt, determined based on the accelerator opening Acc, has a
lower value than that set for the EV running mode turn-off state.
For instance, even at the same accelerator opening Acc, the
demanded output torque map for the EV running mode turn-on state is
altered, as shown in FIG. 10, such that demanded output torque
T.sub.OUTt decreases to a level lower than that for the EV running
mode turn-off state. Therefore, even if the accelerator peal is
depressed in the same way both for the EV running mode turn-on
state and EV running mode turn-off state, demanded output torque
T.sub.OUTt, determined based on the accelerator opening Acc, for
the EV running mode turn-on state has a lower sensitivity than that
of demanded output torque T.sub.OUTt for the EV running mode
turn-off state. This results in the suppression of the occurrence
of engine startup.
Further, the property alter means 88 may alter the given property
for the EV running mode turn-on state based on the vehicle speed V.
For instance, the property alter means 88 alters the given property
so as to decrease demanded output torque T.sub.OUTt, determined
based on the accelerator opening Acc, as the vehicle speed V
decreases. For instance, even at the same accelerator opening Acc,
the property alter means 88 alters the demanded output torque map
for the EV running mode turn-on state such that with decrease of
the vehicle speed V, demanded output torque T.sub.OUTt decreases as
shown in FIG. 10.
Thus, even if the accelerator pedal is depressed for the EV running
mode turn-on state in the same way during the EV running mode,
demanded output torque T.sub.OUTt, determined based on the
accelerator opening Acc, can have a sensitivity decreasing with
decrease of the vehicle speed under a situation where a stronger
requirement occurs for the EV running mode to be initiated in an
area with a further worrisome engine sound in concern. This results
in the suppression of the occurrence of engine startup.
It is conceived that in an area wherein the vehicle runs at a
middle and high speed, a relatively less concern is present for the
engine sound and instead stronger concern is present for power
performance. With this in mind, the given property may be altered
such that demanded output torque T.sub.OUTt, determined based on
the accelerator opening Acc, has the same sensitivity as that of
demanded output torque T.sub.OUTt for the EV running mode turn-off
state. That is, the property alter means 88 alters the given
property such that with increase of the vehicle speed V, demanded
output torque T.sub.OUTt, determined based on the accelerator
opening Acc approximates demanded output torque T.sub.OUTt for the
EV running mode turn-off state.
For instance, the demanded output torque map shown in FIG. 10 is
altered such that for the EV running mode turn-on state, demanded
output torque T.sub.OUTt at the same accelerator opening Acc
approaches demanded output torque T.sub.OUTt for the EV running
mode turn-off state as the vehicle speed V increases. With such
alteration, even if the EV running mode turn-on state is present,
the EV running mode can be continuously executed in a low vehicle
speed range as required by the driver without sacrificing power
performance in the middle and high vehicle speed range.
FIG. 11 is a view showing one example of the relationship
(sensitivity function map) between a sensitivity function .rho. and
a vehicle speed V that is preliminarily obtained on experiments for
storage. The sensitivity function is used for obtaining demanded
output torque T.sub.OUTt for the EV running mode turn-on state upon
multiplying demanded output torque T.sub.OUTt for the EV running
mode turn-off state by the sensitivity function. This is because
demanded output torque T.sub.OUTt, determined based on the
accelerator opening Acc, for the EV running mode turn-on state is
required to have a lower sensitivity than that of demanded output
torque T.sub.OUTt for the EV running mode turn-off state.
In FIG. 11, the sensitivity map is set so as to decrease the
sensitivity function .rho. as the vehicle speed decreases such that
demanded output torque T.sub.OUTt, determined based on the
accelerator opening Acc has the sensitivity decreasing as the
vehicle speed decreases. With the vehicle speed V beyond a given
vehicle speed V', the sensitivity function .rho. is set to a value
of "1". This is because demanded output torques T.sub.OUTt,
determined based on the accelerator opening Acc lay at the same
value both for the EV running mode turn-on state and EV running
mode turn-off state. As used herein, the term "given vehicle speed
V" refers to a determination vehicle speed, preliminarily obtained
on experiments, which represents a vehicle speed at which demanded
output torque T.sub.OUTt determined based on the accelerator
opening Acc for the EV running mode turn-on state, is made equal to
demanded output torque T.sub.OUTt for the EV running mode turn-off
state. This is because for the EV running mode turn-on state, a
relatively less concern is present for the engine sound and instead
stronger concern is present for power performance.
FIGS. 12A and 12B are views showing demanded output torque maps
similar to that shown in FIG. 10. FIG. 12A represents one example
of the demanded output torque map for a case in which the vehicle
speed V belongs to a low vehicle speed region to be less than the
given vehicle speed V'. FIG. 12B represents another example of the
demanded output torque map for a case in which the vehicle speed V
belongs to a middle and high vehicle speed region to be higher than
the given vehicle speed V'.
In FIG. 12A, a solid line represents the demanded output torque map
for the EV running mode turn-off state which has a property
equivalent to, for instance, the demanded output torque map shown
in FIG. 10. In addition, a double-dot line represents the demanded
output torque map for the EV running mode turn-on state which has a
property obtained by multiplying the demanded output torque map for
the EV running mode turn-off state by the sensitivity function
.rho., shown in FIG. 11, i.e., for instance, a sensitivity function
.rho.1 for a vehicle speed V1.
As will be apparent from FIG. 12A, if, for instance, the
accelerator pedal is depressed during the EV running mode and the
accelerator opening Acc lies at a given accelerator opening Acc1,
demanded output torque T.sub.OUT lies at a given value T.sub.OUT1
for the EV running mode turn-off state. In this moment, the vehicle
condition is caused to vary from the EV running region to the
engine running region to start up the engine 8. In contrast, during
the EV running mode turn-on state, demanded output torque T.sub.OUT
becomes less than the given value T.sub.OUT1 with the vehicle
condition remained unchanged in the EV running region. Therefore,
no startup of the engine 8 occurs and the EV running mode is
sustained.
In FIG. 12B, a solid line represents the demanded output torque map
for the EV running mode turn-off state similar to the demanded
output torque map shown in FIG. 12A. However, under a situation
where the vehicle speed V increases beyond the given vehicle speed
V', the property alter means 88 uses the same demanded output
torque map as that for the EV running mode turn-off state even in
the EV running mode turn-on state. Therefore, in the middle and
high vehicle speed region where the vehicle speed V exceeds the
given vehicle speed V', the drive system ensures power performance
equivalent to that for the EV running mode turn-off state.
During the EV running mode turn-on state, for instance, if vehicle
speed determination means 92 determines that the vehicle speed V is
less than the given vehicle speed V', the proper alter means 88
calculates the sensitivity function .rho. based on an actual
vehicle speed V by referring to the sensitivity function map shown
in FIG. 11. Multiplying the demanded output torque map for the EV
running mode turn-off state by the sensitivity function .rho.
allows the demanded output torque map to be set for the EV running
mode turn-on state.
The demanded drive-force relevant value calculation means 86
calculates the demanded output torque T.sub.OUT based on an actual
accelerator opening Acc by referring to the demanded output torque
map for the EV running mode turn-on state.
In contrast, during the EV running mode turn-off state or the EV
running mode turn-on state, if the vehicle speed determination
means 92 determines that the vehicle speed V is higher than the
given vehicle speed V', the demanded drive-force relevant value
calculation means 86 calculates demanded output torque T.sub.OUT
based on the actual accelerator opening Acc by referring to the
demanded output torque map for the EV running mode turn-off
state.
If demanded output torque T.sub.OUT, calculated by the demanded
drive-force relevant value calculation means 86, is less than the
given value T.sub.OUT1 with the vehicle condition remained under
the EV running region, then the hybrid control means 84 drives only
the second electric motor M2 so as to obtain relevant demanded
output torque T.sub.OUT thereby executing the EV running mode. On
the contrary, if demanded output torque T.sub.OUT calculated by the
demanded drive-force relevant value calculation means 86, exceeds
the given value T.sub.OUT1 with the vehicle condition remained
under the engine running region, then the hybrid control means 84
allows the engine 8 to start up so as to obtain relevant demanded
output torque T.sub.OUT thereby executing the engine running
mode.
FIG. 13 is a flowchart illustrating a basic sequence of major
control operations to be executed by the electronic control unit
80, i.e., a basic sequence of control operations to be executed for
suppressing the occurrence of engine startup to comply with the
request on the EV running mode. This sequence is repeatedly
executed for extremely short cycles each of the order of
approximately, for instance, several milliseconds to several tens
milliseconds.
First, in step (hereinafter the term "step" will be omitted) S1
corresponding to the EV running mode determination means 90, the
operation is executed to determine whether or not the EV running
mode is set, i.e., for instance, based on whether or not the EV
running mode switch 72 remains in a turn-on state.
If the determination in S1 is made positive, then in S2
corresponding to the vehicle speed determination means 92, the
determination is made whether or not the vehicle speed V is less
than the given vehicle speed V'.
If the determination in S2 is made positive, then in S3
corresponding to the property alter means 88, the sensitivity
function .rho. is calculated based on the actual vehicle speed V by
referring to the sensitivity function map for instance as shown in
FIG. 11. Multiplying the demanded output torque map for the EV
running mode turn-off state, for instance, as shown in FIG. 12, by
the sensitivity function .rho. allows the demanded output torque
map to be set for the EV running mode turn-on state.
In S4 corresponding to the demanded drive-force relevant value,
calculation means 86 in sequence subsequent to S3, demanded output
torque T.sub.OUT is calculated. This similarly applies to a case
wherein the determination in S1 is made negative or the
determination in S2 is made negative. For instance, if both the
determinations in S1 and S2 are made positive, demanded output
torque T.sub.OUT is calculated based on the actual accelerator
opening Acc by referring to the demanded output torque map for the
EV running mode turn-on state set in S3.
On the contrary, if both the determinations in S1 and S2 are made
negative, demanded output torque T.sub.OUT is calculated based on
the actual accelerator opening Acc by referring to the demanded
output torque map for the EV running mode turn-off state as shown
in FIGS. 12A and 12B.
If demanded output torque T.sub.OUT calculated in S4 is less than
the given value T.sub.OUT1 with the vehicle condition remains under
the EV running region, in succeeding S5 corresponding to the hybrid
control means 84, only the second electric motor M2 is driven to
execute the EV running mode. This allows relevant demanded output
torque T.sub.OUT to be obtained. In contrast, if demanded output
torque T.sub.OUT calculated in S4 exceeds the given value
T.sub.OUT1 and the vehicle condition crosses the EV running region
to the engine running region, then, the engine 8 is caused to start
up to execute the engine running mode. Thus, relevant demanded
output torque T.sub.OUT is obtained.
In the illustrated embodiment, as set forth above, the property
alter means 88 alters the given property used for determining
demanded output torque T.sub.OUTt of the transmission mechanism 10
based on the accelerator opening Acc depending on whether or not
the EV running mode is set. This enables the suppression of the
occurrence of engine startup to comply with the request on the EV
running mode. For instance, during the EV running mode turn-on
state, the property alter means 88 alters the given property such
that demanded output torque T.sub.OUT, determined based on the
accelerator opening Acc, for the EV running mode turn-on state lies
at a lower level than that for the EV running mode turn-off state.
That is, this causes a drop in sensitivity of demanded output
torque T.sub.OUT determined based on the accelerator opening Acc.
This results in a consequence of suppressing the occurrence of
engine startup that would be induced upon the depressing operation
of the accelerator pedal during the EV running mode.
In the illustrated embodiment, the property alter means 88 can
alter the given property based on the vehicle speed V during the EV
running mode turn-on state. This enables the suppression of the
occurrence of engine startup depending on the vehicle speed V. For
instance, the property alter means 88 alters the given property
such that as the vehicle speed V decreases, demanded output torque
T.sub.OUTt, determined based on the accelerator opening Acc,
decreases. This suppresses the occurrence of engine startup during
the EV running mode under a circumstance where the vehicle runs at
a low speed in a residential area or the like with a worrisome
engine sound in concern in the presence of a stronger demand for
the EV running mode.
In the illustrated embodiment, the property alter means 88 can
alter the given property such that as the vehicle speed V
increases, demanded output torque T.sub.OUTt determined based on
the same accelerator opening Acc, approximates demanded output
torque T.sub.OUT for the EV running mode turn-off state. Therefore,
even during the EV running mode turn-on state, under a circumstance
where the vehicle runs at the middle and high vehicle speed with a
stronger demand present for power performance, relevant power
performance can be caused to approach excellent power performance
attained with the EV running mode turn-off state. That is, the EV
running mode can be continued in the low vehicle speed region as
required by the driver without sacrificing power performance in the
middle and high vehicle speed region.
Next, another embodiment according to the present invention will be
described below. Also, in the following description, the same
component parts common to those used in various embodiments bear
like reference numerals to omit descriptions of the same
Embodiment 2
Second embodiment will be explained with reference to FIGS. 14 to
16. FIG. 14 is a skeleton view illustrating a structure of a
transmission mechanism 100 of another embodiment according to the
present invention. FIG. 15 is an engagement operation diagram
representing combined operations of hydraulically operated
frictional engaging devices for use in shifting operations of the
transmission mechanism 100. FIG. 16 is a collinear chart
illustrating the shifting operations of the transmission mechanism
100.
Like the first embodiment, the transmission mechanism 100 includes
the differential portion 11 comprised of the first electric motor
M1, the power transmitting mechanism 16 and the second electric
motor M2, and a forward-drive three-stage automatic transmission
portion 102 connected between the differential portion 11 and the
output shaft 22 in series via the power transmitting member 18. The
power transmitting mechanism 16 includes the single-pinion type
first planetary gear set 24 having the given gear ratio .rho.1 of
approximately, for instance, "0.418". The automatic transmission
portion 102 includes the single-pinion type second planetary gear
set 26 having the given gear ratio .rho.2 of approximately, for
instance, "0.532" and single-pinion type third planetary gear set
28 having the given gear ratio .rho.3 of approximately, for
instance, "0.418".
The second and third planetary gear sets 26 and 28 have the second
and third sun gears S2 and S3, respectively, which are unitarily
connected to each other and selectively connected to the power
transmitting member 18 and the casing 12 via the second clutch C2
and first brake B1, respectively. The second and third planetary
gear sets 26 and 28 have the second carrier CA2 and third ring gear
R3, respectively, which are unitarily connected to each other and
connected to the output shaft 22. The second ring gear R2 is
connected to the power transmitting member 18 via the first clutch
C1 and the third carrier CA3 is selectively connected to the casing
12 via the second brake B2.
Thus, the internal component parts of the automatic transmission
portion 102 and the differential portion 11 (power transmitting
member 18) are selectively connected to each other via the first
and second clutches C1 and C2 for causing the automatic
transmission portion 102 to establish the gear position. In other
words, the first and second clutches C1 and C2 function as coupling
devices for selectively switching the power transmitting path
between the power transmitting member 18 and automatic transmission
portion 102, i.e., the power transmitting path between the
differential portion 11 (power transmitting member 18) and drive
wheels 18 in one of a power transmitting state and power cut-off
i.e., interrupted state. That is, upon coupling at least one of the
first and second clutches C1 and C2, the power transmitting path is
placed in the power transmitting state. In contrast, upon
uncoupling the first and second clutches C1 and C2, the power
transmitting path is placed in the power cut-off state.
With the automatic transmission portion 102, uncoupling the
on-uncoupling side coupling device and coupling the on-coupling
side coupling device allows the clutch-to-clutch shift to be
executed for selectively establishing the various gear positions
(gear shift positions). This enables each gear position to be
obtained with the gear ratio .gamma. (=transmitting-member rotation
speed N.sub.18/output-shaft rotation speed N.sub.OUT) in nearly
equal ratio. As represented by the engagement operation table shown
in FIG. 15, for instance, coupling the first clutch C1 and second
brake B2 allows the 1st-speed gear position to be established with
a gear ratio .gamma.1 in a maximal value of approximately, for
instance, "2.804". Coupling the first clutch C1 and first brake B1
allows a 2nd-speed gear position to be established with a gear
ratio .gamma.2 of approximately, for instance, "1.531" less than
that of the 2nd-speed gear position. Coupling the first and second
clutches C1 and C2 allows a 3rd-speed gear position to be
established with a gear ratio .gamma.3 of approximately, for
instance, "1.000" less than that of the 2nd-speed gear
position.
Coupling the second clutch C2 and second brake B2 allows a
reverse-drive gear position (reverse-drive gear shift position) to
be established with a gear ratio .gamma.R of approximately, for
instance, "2.393" intermediate in value between the 1st- and
2nd-speed gear positions. In addition, uncoupling the first and
second clutches C1 and C2 and first and second brakes B1 and B2
allows a neutral position "N" to be established. Moreover, as
indicated by the engagement operation table shown in FIG. 15, the
coupling devices of the automatic transmission portion 20 are
operated for a 4th-speed gear position under the same engagement
operations as those of the coupling devices operated for a
3rd-speed position.
With the transmission mechanism 100 of such a structure mentioned
above, the differential portion 11 functioning as the continuously
variable transmission, and the automatic transmission portion 102
constitute the continuously variable transmission. In addition,
controlling the differential portion 11 to maintain the speed ratio
at a fixed level enables the differential portion 11 and automatic
transmission portion 102 to form a state equivalent to a
step-variable transmission.
More particularly, the differential portion 11 functions as the
continuously variable transmission, and the automatic transmission
portion 102 connected to the differential portion 11 in series
functions as the step-variable transmission. This allows a rotation
speed (hereinafter referred to as an input rotation speed of the
automatic transmission portion 102), i.e., a rotation speed of the
power transmitting member 18, to be input to the automatic
transmission portion 102 at a steplessly i.e., continuously varying
rate for at least one shift position M of the automatic
transmission portion 102. This causes the shift position M to have
a continuously variable speed ratio in shifting. Accordingly, the
transmission mechanism 100 has an overall speed ratio .gamma.T in
an infinitely variable range, causing the transmission mechanism
100 to form a continuously variable transmission.
Thus, the transmitting-member rotation speed N.sub.18 is caused to
continuously vary for each of the various gear positions of the
1st- to 3rd-speed gear positions and reverse-drive gear position of
the automatic transmission portion 102. This causes each gear
position to continuously vary in speed ratio as indicated, for
instance, by the engagement operation table shown in FIG. 5.
Consequently, an intermediate position between the adjacent gear
positions is steplessly or continuously variable in speed ratio,
causing the transmission mechanism 100 as a whole to have a total
speed ratio .gamma.T in an infinitely variable rate.
Upon operation of the differential portion 11 controlled at a fixed
speed ratio with the clutch C and brake B selectively coupled,
either one of the 1st- to 3rd-speed gear positions or the
reverse-drive gear position (reverse-drive gear shift position) is
selectively established. When this takes place, the total speed
ratio .gamma.T of the transmission mechanism 100 is variable in a
nearly equal ratio i.e., geometrically for each gear position.
Accordingly, the transmission mechanism 100 can establish a state
equivalent to the step-variable transmission.
With the differential portion 11 controlled to have a gear ratio
.gamma.0 fixed at a value of "1", for instance, the transmission
mechanism 100 has a total speed ratio .gamma.T for each of the gear
positions corresponding to the 1st- to 3rd-speed gear positions and
reverse-drive gar position of the automatic transmission portion
102, as indicated by the engagement operation table shown in FIG.
15. In addition, with the automatic transmission portion 102 placed
in the 3rd-speed gear position, if the differential portion 11 is
controlled to have a gear ratio .gamma.0 fixed at a value of
approximately, for instance, "0.7" less than a value of "1", the
transmission mechanism 100 has a total speed ratio .gamma.T in a
value of approximately, for instance, "0.705" that is less than a
value of the 3rd-speed gear position as indicated by the 4th-speed
gear position in the engagement operation table shown in FIG.
15.
FIG. 16 shows a collinear chart for the transmission mechanism 100,
comprised of the differential portion 11 and automatic transmission
portion 102, which has straight lines plotted for the relative
motion relationships among the rotation speeds of the various
rotary elements placed in different coupling states for each gear
position.
Starting from the left in sequence, four vertical lines Y4 to Y7
represent: rotation speeds of the second and third sun gears S2 and
S3 corresponding to the fourth rotary element (fourth element) RE4
and connected to each other; a rotation speed of the third carrier
CA3 corresponding to the fifth rotary element (fifth element) RE5;
rotation speeds of the second carrier CA2 and third ring gear R3
and S3 corresponding to the sixth rotary element (sixth element)
RE4 and connected to each other; and a rotation speed of the second
ring gear R2 corresponding to the seventh rotary element (seventh
element), respectively.
With the automatic transmission portion 102, the fourth rotary
element RE4 is selectively connected to the power transmitting
member 18 and casing 12 via the second clutch C2 and first brake
B1, respectively. The fifth rotary element RE5 is selectively
connected to the casing 12 via the second brake B2. The sixth
rotary element RE6 is connected to the output shaft 22 of the
automatic transmission portion 102 and the seventh rotary element
RE7 is selectively connected to the power transmitting path 18 via
the first clutch C1.
In the automatic transmission portion 102, if the straight line L0
is caused to match the horizontal line X2 in the differential
portion 11 and the differential portion 11 inputs a rotary motion
to the seventh rotary element RE7 at the same rotation speed as the
engine rotation speed N.sub.E, the first clutch C1 and second brake
B2 are coupled as indicated in FIG. 16. In this case, a rotation
speed of the output shaft 22 for the 1st-speed gear position is
indicated by an intersecting point between an inclined line L1,
passing across an intersecting point between the vertical line Y7
representing the rotation speed of the seventh rotary element RE7
(R2), and the horizontal line X2 and an intersecting point between
the vertical line Y5 representing the rotation speed of the fifth
rotary element RE5 (CA3), and the horizontal line X1, and the
vertical line Y6 representing the rotation speed of the sixth
rotary element RE6 (CA2 and R3) connected to the output shaft
22.
Likewise, a rotation speed of the output shaft 22 for the 2nd-speed
gear position is indicated by an intersecting point between an
inclined straight line L2 determined with the first clutch C1 and
first brake B1 being coupled, and the vertical line Y6 representing
the sixth rotary element RE6 connected to the output shaft 22. A
rotation speed of the output shaft 22 for the 3rd-speed gear
position is indicated by an intersecting point between a horizontal
line L3, determined with the first and second clutches C1 and C2
being coupled, and the vertical line Y6 representing the sixth
rotary element RE6 connected to the output shaft 22.
In the differential portion 11, if the straight line L0 is placed
in a state shown in FIG. 16 with the differential portion 11
inputting a rotary motion to the seventh rotary element RE7 at a
rotation speed higher than the engine rotation speed N.sub.E, a
rotation speed of the output shaft 22 for the 4th-speed gear
position is indicated by an intersecting point between a horizontal
line L4 determined with the first and second clutches C1 and C2
being coupled, and the vertical line Y6 representing the rotation
speed of the sixth rotary element RE6 connected to the output shaft
22 as shown in FIG. 6.
Even in the second illustrated embodiment, the transmission
mechanism 100 is structured of the differential portion 11 and the
automatic transmission portion 102 with the same advantageous
effect as those of the first embodiment.
In the foregoing, while the present invention has been described
with reference to the embodiments shown in the drawings, it is to
be appreciated that the present invention may be implemented in
combination of the various embodiments and in other
modifications.
In the illustrated embodiments, for instance, if the vehicle speed
V is less than the given vehicle speed V' during the EV running
mode turn-on state, the demanded output torque map for the EV
running mode turn-on state is set upon multiplying the demanded
output torque map for the EV running mode turn-off state by the
sensitivity function .rho. that varies depending on the vehicle
speed. However, the demanded output torque map for the EV running
mode turn-on mode may be preliminarily obtained and stored on
experiments in terms of a parameter of the vehicle speed V such
that as the vehicle speed decreases, demanded output torque
T.sub.OUT decreases. In such a case, no need arises for calculating
the sensitivity function .rho. by referring to the sensitivity
function map and no sensitivity function map is required in
nature.
In the illustrated embodiment discussed above, the hybrid vehicle
to which the present invention is applied has been exemplified as
having the transmission mechanism 10. However, the present
invention is not limited to such a concept and a power-drive source
may be employed for a vehicle to be driven and include an electric
motor, operating on electric energy, and an engine operating on
fuel combustion. The present invention may have an application to a
hybrid vehicle formed in such a structure that is operative based
on a vehicle condition, such as demanded output torque or the like,
whereby the vehicle condition is switched between an EV running
mode depending on a drive-power source composed of only an electric
motor, and an engine running mode depending on another drive-power
source mainly composed of an engine.
In the illustrated embodiment set forth above, the differential
portion 11 (power distributing mechanism 16) is configured to
function as the electrically controlled continuously variable
transmission in which the speed ratio y0 is continuously varied
from the minimal value .gamma.0.sub.min to the maximal value
.gamma.0.sub.max. However, the present invention may be applied
even to a case wherein the speed ratio .gamma.0 of the differential
portion 11 is not continuously varied but pretended to vary
step-by-step with the use of a differential action.
In the illustrated embodiment set forth above, the differential
portion 11 may be of the type that includes a differential action
limiting device incorporated in the power distributing mechanism 16
for limiting a differential action to be operative as at least a
forward two-stage step-variable transmission.
With the power distribution mechanisms 16 of the illustrated
embodiments, the first carrier CA1 is connected to the engine 8,
the first sun gear S1 is connected to the first electric motor M1
and the first ring gear R1 is connected to the power transmitting
member 18. However, the present invention is not necessarily
limited to such connecting arrangement and the engine 8, first
electric motor M1 and power transmitting member 18 have no
objection to be connected to either one of the three elements CA1,
S1 and R1 of the first planetary gear set 24.
Although the illustrated embodiment has been described with
reference to the engine 8 directly connected to the input shaft 14,
these component parts may suffice to be operatively connected via,
for instance, gears, belts or the like and no need arises for these
component parts to be necessarily disposed on a common axis.
In the illustrated embodiment, with the first electric motor M1 and
second electric motor M2, the first electric motor M1 coaxially
connected to the input shaft 14 is connected to the power
transmitting member 18 to which the second electric motor M2
connected to the first sun gear S1, is connected. However, no need
arises for these component parts to be necessarily placed in such
connecting arrangement. For example, the first electric motor M1
may be connected to the first sun gear S1 through gears, a belt or
the like, and the second electric motor M2 may be connected to the
power transmitting member 18.
In the illustrated embodiment, the hydraulically operated
frictional coupling devices such as the first and second clutches
C1 and C2 may include magnetic type clutches such as powder
(magnetic powder) clutches, electromagnetic clutches and meshing
type dog clutches, and electromagnetic type and mechanical coupling
devices. For instance, with the electromagnetic clutches being
employed, the hydraulic control circuit 70 may not include a valve
device for switching hydraulic passages and may be replaced with a
switching device or electromagnetically operated switching device
or the like that are operative to switch electrical command signal
circuits for electromagnetic clutches.
In the illustrated embodiment, each of the automatic transmission
portions 20 and 102 is disposed in the power transmitting path
between the power transmitting member 18 serving as the output
member of the differential portion 11, i.e., the power distributing
mechanism 16 and the drive wheels 34. However, the power
transmitting path may incorporate a power transmission portion
(transmission) of other type. For instance, this may include a
continuously variable transmission (CVT) acting as an automatic
transmission of one kind, and an automatic transmission or the like
including a constant-mesh type parallel shaft transmission, well
known as a manual shift transmission, and including an automatic
transmission composed of select cylinders and shift cylinders to
automatically switch gear positions, and a manual transmission or
the like of a synchronizing mesh type in which the gear positions
are manually shifted.
In the illustrated embodiment, each of the automatic transmission
portions 20 and 102 is connected to the differential portion 11 in
series via the power transmitting member 18. However, a
countershaft may be provided in parallel to the input shaft 14 and
each of the automatic transmission portions 20 and 102 may be
coaxially disposed on an axis of the countershaft. In this case,
the differential portion 11 and each of the automatic transmission
portions 20 and 102 may be connected to each other in power
transmitting capability via a set of transmitting members
structured of, for instance, a counter-gear pair acting as the
power transmitting member 18, and a sprocket and chain.
The power distributing mechanism 16 serving as the differential
mechanism in the illustrated embodiment, may include for instance a
differential gear set in which a pinion rotatably driven with the
engine, and a pair of bevel gears held in meshing engagement with
the pinion are operatively connected to the first electric motor M1
and the power transmitting member 18 (second electric motor
M2).
The power distributing mechanism 16 of the illustrated embodiment
has been described above as including one set of planetary gear
units. However, the power distributing mechanism 16 may include two
or more sets of planetary gear units that are arranged to function
as a transmission having three or more speed positions under a
non-differential state (fixed shifting state). In addition, the
planetary gear unit is not limited to the single-pinion type, but
may be of a double-pinion type.
The shift operation device 50 of the illustrated embodiment has
been described with reference to the shift lever 52 operative to
select a plurality of kinds of shift positions P.sub.SH. However,
the shift lever 52 may be replaced by other type of switch or
device. These may include, for instance: a select switch such as a
press-button type switch and a slide-type switch or the like
available to select one of a plurality of shift positions P.sub.SH;
a device operative to switch a plurality of shift positions
P.sub.SH in response not to the manipulation initiated by the hand
but to a driver's voice; and a device operative to switch a
plurality of shift positions P.sub.SH in response to the
manipulation initiated by the foot.
Like the illustrated embodiment described above, shifting the shift
lever 52 to the "M" position allows shift positions to be set,
i.e., the highest speed gear position for each shift range to be
set in place of setting the shifting range. In this case, each of
the automatic transmission portions 20 and 102 allows the shift
position to be switched for executing the shifting action. For
example, as the shift lever 52 is manually operated to an upshift
position "+" or a downshift position "-" in the "M" position, the
automatic transmission portion 20 allows any of the 1st-speed gear
position to the 4th-speed gear position to be set depending on a
manipulated position of the shift lever 52.
The foregoing merely illustrates the embodiments for illustrating
the principles of the present invention. It will be appreciated by
those skilled in the art that various modifications and
alternatives to those details could be developed in the light of
the overall teachings of the disclosure.
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